The best open source alternative to XYplorer is Double Commander, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 50 alternatives to XYplorer and many of them is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to XYplorer are Midnight Commander (Free, Open Source), Dolphin File Manager (Free, Open Source), Thunar (Free, Open Source) and Far Manager (Free, Open Source).
Dolphin is a file manager for KDE focusing on usability. Has three view modes: Icon, Detail and it used to have Column View like in Finder (it is not available in current version due to problems with maintaibility). Supports FTP, SCP and other protocols. Highly configurable.
Thunar is a new modern file manager for the Xfce Desktop Environment. Thunar has been designed from the ground up to be fast and easy-to-use. Its user interface is clean and intuitive, and does not include any confusing or useless options.
Meet Files, an enthusiast take on what Windows File Explorer explorer should be. Files is the modern file manager you always wanted. It's packed with features such as fluent design, tabs, layout modes, and much more.
Explorer++ is a free file manager for Windows. Available on Windows XP and above, it features the same familiar interface as Windows Explorer, while introducing several enhancements and improvements for a much richer file browsing experience.